Communication-enabled devices such as laptops, mobile terminals and personal computers can be connected to further devices and each other via wired or wireless connections. A local-area network, LAN, may function based on the Ethernet standard, for example, to connect a group of personal computers into a local network. A local network may comprise devices that are addressable to each other using addresses that are routable, or valid, in the context of the local network. In other words, a message released into a local network comprising as a to-address a local address of a first device will be routed internally in the local network to the first device. A message comprising the same local address as to-address released into a network outside the local network will not be successfully routed to the first device since the local address is not valid outside the local network.
A local network may be connected to an external network, such as the internet, through a gateway disposed between the local network and the external network. Being disposed between the networks may comprise that the gateway has an interface to the local network and that the gateway has an interface to the external network. These interfaces may be referred to as a local interface and global interface, respectively.
The gateway may be configured to handle addressing between the networks so that a device sending a message to a node in the external network may release the message into the local network with a local address of the local interface of the gateway in a to-address field of the message, and upon receipt of the message the gateway may replace its own local address with an address of the node in the external network in the to-address field of the message. In the other direction, the node in the external network may reply to the device in the local network by releasing into the external network a message with an address of the global interface of the gateway in the to-field, and responsive to receiving this message, the gateway may insert the local address of the device in the local network into the to-field, and release the message into the local network via the local interface of the gateway. This kind of address handling may be referred to as network address translation, NAT.
When devices in the local network seek to communicate with each other, they can use local addressing to address each other without a need for address translation. Devices in a same local network may be associated with each other, for example where the local network is a corporate LAN or where the local network is a wireless local area network, WLAN. Devices in a WLAN may be associated with each other by being in physical proximity to each other.
Before devices in the same local network can communicate with each other, they need to become aware of each other. A process of becoming aware may be called a discovery procedure, whereby devices discover each other on a local network. A simple discovery procedure comprises that a user of a first device manually enters a local address of a second device into his device. Other discovery procedures comprise broadcasting in the local network to search for other devices.